Large cellular structures such as cell walls, nuclei, chloroplasts and vacuoles.
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Can the internal structures of organelles be seen with a light microscope?
No
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What two types of electron microscopes are there?
Transmission electron microscopes and scanning electron microscopes
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How do TEM work?
Electrons pass through the material
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How do SEM work?
Electrons are bounced off the surface of the material, giving a 3D view of the surface
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How do laser scanning confocal microscopes work?
Cells are stained with fluorescent dyes, and a thick section of tissue is scanned with a laser beam which is reflected by the dyes. The laser beam is scanned across different depths of the section.
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List two advantages of laser scanning confocal microscopes.
The laser beam can be focused at a very specific depth, eliminating blur. Images can be taken at successive depths and fed into a computer, enabling us to reconstruct a 3D image of the tissue.
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What is Magnification?
The measure of the ability of a lens to enlarge the size of something in an optical image.
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How is resolution different?
Resolution refers to the ability of a microscope to distinguish two adjacent points as separate from each other.
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List the maximum magnifications for each microscope (not laser)
Light: x1500, TEM: x500,000, SEM: x100,000
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List the maximum resolutions for each microscope (not laser)
Light: 200nm, TEM: 0.2nm, SEM: 10nm
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Why do electron microscopes have higher resolution?
Electrons have a much shorter wavelength than light.
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How do you calculate the magnification of an image?
Magnification = size of image/actual size
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How do you calculate the actual size of an object?
Actual size = size of image/magnification
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How do you calculate the size of the image?
Size of image = actual size x magnification
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How does staining for light microscopy work?
The dyes absorb some colours of light and reflect others, making the structures that absorb the dye visible. Different tissues absorb different dyes, according to their chemical nature.
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How does staining for TEM work?
TEM need to use stains that absorb those particles - electrons have no colour, so the dyes make the parts look black or shades of grey.
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Can the internal structures of organelles be seen with a light microscope?
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